This invention relates to the partial oxidation of sulfur-containing liquid hydrocarbonaceous fuel or a slurry of sulfur-containing solid carbonaceous fuel. More specifically it relates to the in-situ removal of sulfur-containing gases and slag from the raw effluent synthesis gas stream produced in a refractory lined free-flow gas generator.
As supplies of petroleum gradually diminish sulfur-containing heavy liquid hydrocarbonaceous fuel and/or sulfur-containing coal which is America's most abundant form of fossil fuel will play an increasingly major role in providing for the nation's energy requirements. One ton of coal contains the same amount of energy as three to four barrels of crude oil. Accordingly, in the future it will become necessary to produce an increasing fraction of liquid and gaseous fuels from these sulfur-containing comparatively low cost fuels. The synthesis, reducing, and fuel gases produced from these sulfur-containing materials contain a comparatively high e.g. from about 0.1 to 2.0 mole % of H.sub.2 S and COS. The desirability for removing, at high temperatures, a major share of the sulfur present in synthesis gas, as generated in a Partial Oxidation Gasification Process, is widely recognized. In particular, removal of sulfur from syngas at high temperatures would improve combined cycle thermal efficiency by eliminating the need for costly cooling of product gases for low temperature acid gas wet scrubbing such as with Selexol or Rectisol. When the synthesis gas is burned as fuel in a gas turbine, it may be unneccesary to remove the last trace of sulfur. Energy savings such as possible through a high temperature desulfurization process can outweigh the need to get an extremely low sulfur content fuel gas. The gas produced by this invention may be used with or without further processing and/or purification as a gaseous fuel or as feedstock for the catalytic synthesis of liquid fuels.
Synthesis gas, fuel gas, and reducing gas may be produced from coal by well known gasification processes. For example, coassigned U.S. Pat. Nos. 3,544,291 and 4,289,502 respectively relate to a process for the partial oxidation of slurries of coal, and to an apparatus for producing cleaned and cooled synthesis gas by the partial oxidation of solid carbonaceous fuel.
The subject invention is an improvement in the art since it permits long time operation of the partial oxidation gas generator without shut-down due to accumulation of slag on metal surfaces in the cooling zone. Further, it is superior to the single-stage mode wherein an iron and calcium containing additive is mixed with the fuel feedstock to the gasifier, such as described in coassigned U.S. Pat. No. 4,668,429, and in U.S. Pat. No. 4,599,955 since lower dosages of calcium can accept more sulfur at the lower temperature in the second reaction zone of the subject invention. Two-stage down-flowing and up-flowing gasification processes are known in the art, including for example U.S. Pat. Nos. 2,801,158; 2,961,310; 3,988,123; 4,436,531; and 4,647,294. However, these processes do not provide for in-situ desulfurization of the product gas. Nor do they provide for the production of supplemental H.sub.2 and carbon oxides in the second reaction zone at an increased rate.